. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 368 Comparative Animal Physiology on the desert he may evaporate 1. per hour.^-^ Output of sweat increases 20 for each 1 ° F. rise in air temperature. Man can withstand very high air temperatures if allowed plenty of water for perspiration.^ In secreting sweat man loses much salt, particularly sodium chloride, and in acclimatiza- tion to high temperatures the chloride concentration in sweat decreases while that in urine increases. In warm moist air, as in the jungle, evaporation is much less than in
. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. 368 Comparative Animal Physiology on the desert he may evaporate 1. per hour.^-^ Output of sweat increases 20 for each 1 ° F. rise in air temperature. Man can withstand very high air temperatures if allowed plenty of water for perspiration.^ In secreting sweat man loses much salt, particularly sodium chloride, and in acclimatiza- tion to high temperatures the chloride concentration in sweat decreases while that in urine increases. In warm moist air, as in the jungle, evaporation is much less than in the desert. A burro working on the desert does not pant and it secretes a sweat which contains little chloride. A panting dog, on the inbULflTION '^(h CJ tOTTon JO OALL SHEEP WOLr &RIZ2LY POLMR 10 IF Fig. 97. Maximum insulation of fur of arctic and tropical mammals as a function of fur thickness. Each dot represents one measurement. Values for aquatic animals are given in air (dots) and in ice water (open circles): values for terrestrial animals are given for air only. The insulating value of medium weight cotton is given by the broken line. From Scholander (unpublished). other hand, evaporates much water from its respiratory tract, and this may result in increased chloride concentration in the blood and in the development of some alkalosis due to the blowing off of CO^."'^ In birds, vaporization occurring as air passes through the air sacs may have a cooling effect. When the body temperature is cooled below "optimum," shivering may begin. 1 his is associated with or follows vasoconstriction and piloerection. Shivering increases oxygen consumption, hence heat production. The abilities to panl and to shiver develop in the young animal during the period when temperature regulation ;'"- '^- When the "thermostat" becomes set. Please note that these images are extracted from scanned page images that may have been digitally
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